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Functional Significance of Late Negative Parietal-Occipital EM Effect

Episodic memory (EM) effects have been observed in ERP, with amplitude differences between old and new events starting around 300 ms, continuing to the recording epoch end. The late Negative EM effect could reflect post-decision visualization processes during retrieval, involving mental imagery creation of visual stimuli. Scalp topography of EM effects shows differences in Parietal EM (415-615 ms) and Occipital Parietal EM (700-950; 955-1200 ms). While the Parietal EM effect is clear in both Inclusion and Exclusion tasks, the Late EM effect is prominent only in the Exclusion task. The negative late EM effect may signify reactivation of brain areas responsible for revisiting previously studied visual information. Research examines if the nature of source information (perceptual vs. conceptual) influences scalp distribution of the late Negative EM effect.

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Functional Significance of Late Negative Parietal-Occipital EM Effect

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  1. The Functional Significance of the Late Negative Parietal-Occipital EM Effect Yael M. Cycowicz

  2. Thanks to Michael Bersick Charles Brown David Friedman Cort Horton Letecia Latif

  3. Episodic Memory Episodic memory (EM) effects have been demonstrated in the ERP as a series of amplitude differences between old and new events beginning at about 300 ms and often continuing to the end of the recording epoch.

  4. Late Onset EM Effects • Retrieval Success • Post Retrieval processes • Strategic processes • Monitoring • Evaluation • Response related processes • Monitoring and evaluation of modality specific information Right prefrontal Symmetrical Posterior

  5. The Symmetrical posterior EM effect Is it possible that the late Negative EM effect reflects post-decision visualization processes? Participants may have tried to reinstate the original learning episode which could have involved creating mental images of the visual stimuli, resulted in activity at scalp regions overlying visual cortical areas.

  6. Study 2s Tests Red Green Exclusion Inclusion 2s 2s New Old Other Red

  7. Performance

  8. Parietal EM Parietal EM Parietal Occipital EM

  9. Scalp Topography of EM Effects Parietal EM 415-615 ms Occipital Parietal EM 700-950; 955-1200 ms Inclusion Test Exclusion Test Δ = 0.30 µV

  10. Results Summary • RT old < RT new in the Inclusion task • RT old > RT new in the Exclusion task • Parietal EM effect is clear in both Inclusion and Exclusion tasks • Late EM effect only in the Exclusion task • Late EM effect is large and wide spread over the scalp

  11. Parietal EM Parietal EM Parietal Occipital EM Parietal Occipital EM

  12. POE Parietal EM Parietal EM Parietal Occipital EM

  13. Conclusions The negative late EM effect reflects: Reactivation of brain areas supporting recapitulation of previously studied Colored Pictures Retrieval and/or evaluation of perceptual visual information (color) may be modality specific and thus elicited activity in visual cortex.

  14. Research Questions Does the nature of the source information (perceptual vs. conceptual) can affect the scalp distribution of the late negative EM effect ? If so, can we better understand the functional significance of the late negative EM effect ?

  15. Conceptual Source Atypical Typical

  16. Study 2s Tests Exclusion Inclusion 2s 2s New Old Other

  17. Performance

  18. Parietal EM Parietal EM Parietal Occipital EM

  19. Scalp Topography of EM Effects Parietal EM 415-615 ms Occipital Parietal EM 700-950; 955-1200 ms Inclusion Test Exclusion Test Δ = 0.30 µV

  20. Results Summary • RT old < RT new in the Inclusion task • RT old > RT new in the Exclusion task • Parietal EM effect is clear in both Inclusion and Exclusion tasks • Late EM effect only in the Exclusion task • Late EM effect is smaller and shorter than previously reported • Late EM effect has a different scalp distribution than those previously reported

  21. Scalp Topography of EM Effects Parietal EM 415-615 ms Occipital Parietal EM 700-950; 955-1200 ms Inclusion Test Conceptual Exclusion Test Perceptual Δ = 0.30 µV

  22. Summary • Retrieval of Conceptual information elicited a small late occipital negative EM effect • In the preliminary analysis no other late effects can be detected

  23. Conclusions The magnitude and distribution of the late occipital negativity is modulated by the type of source attribute Differences in retrieval processes are affected by differences in encoding processes

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